Ukraine's military said today that Russia had given its forces an ultimatum to surrender in Crimea or face an all-out assault on the strategic Black Sea peninsula that has been overrun by Kremlin-backed troops.
But Russia's Black Fleet swiftly denied any such demand and the country's parliament speaker said there was no need yet for Moscow to use its "right" to launch military action in Ukraine.
"The ultimatum is to recognise the new Crimean authorities, lay down our weapons and leave, or be ready for an assault," regional Ukrainian defence ministry spokesman Vladyslav Seleznyov told AFP in the Crimean capital Simferopol.
"It may be at 1:00 am, 2:00 am, 3:00 am (Tuesday). There are different times," he said.
Ukraine has accused Russia of pouring more troops into Crimea as world leaders grappled with Europe's worst standoff since the Cold War.
Crimea -- the strategic host to tsarist and Kremlin navies since the 18th century -- has been under de facto occupation by Moscow-backed forces who have raised Russian flag over government buildings and blocked Ukrainians troops inside their barracks across the peninsula.
The new leaders in Kiev branded Russia's actions a declaration of "war" and jittery global markets plunged on Monday over fears of a conflict while the price of oil surged.
The Moscow market alone at one stage lost 13 per cent on a Black Monday of trading that saw the ruble hit historic lows.
World leaders were holding a series of urgent meetings and telephone conversations to try to avert a conflict and also to help Ukraine avert a possible catastrophic debt default.
